In several earlier patents of common inventorship to this application there have been revealed teaching apparatus wherein illuminable indicators serve to identify individual notes which when sounded together form a triad. These U.S. Pat. Nos. include the following:
3,335,630-- ISSUED Aug. 15, 1967; 3,503,296-- issued Mar. 31, 1970; 3,503,297-- issued Mar. 31, 1970; 3,664,036-- issued May 23, 1970; 3,897,710-- issued Aug. 5, 1975.
While the above-identified patents disclose teaching apparatus which, in some instances, may be utilized apart from the musical instrument itself, they are primarily designed for instruction in the actual manipulation of keys of a keyboard musical instrument where the student is manipulating the keys so as to sound the instrument at the same time that he is receiving instructional stimulus from the illuminable display.